Treatment of hydrocarbon containing reservoirs with electrolyzed water

ABSTRACT

Systems and methods for using one or more electrolyzed aqueous solutions to treat subterranean reservoirs containing hydrocarbons are disclosed herein. In some cases, the methods include using an electrochemical cell to produce electrolyzed acidic water and electrolyzed alkaline water. In such cases, the electrolyzed acidic water or the electrolyzed alkaline water is introduced to the well. While the electrolyzed acidic or alkaline water can be used for a variety of purposes, in some cases, it is used to improve hydraulic fracturing, water flooding, and well stimulation techniques. In some cases, the electrolyzed acidic or alkaline water is mixed with one or more other materials, such as a proppant, a hydraulic fracturing fluid, a polymer, or another additive. Additional implementations are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/507,458, filed Jul. 13, 2011, entitled “Treatment of HydrocarbonContaining Petroleum Reservoirs with Electrolyzed Water,” the entiredisclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to systems and methods for enhanced recovery ofhydrocarbons from a hydrocarbon containing reservoir. More specifically,in some implementations, this invention relates to the use ofelectrolyzed water for hydraulic fracturing, water flooding, wellstimulation, and other processes that can improve recovery of ahydrocarbon (such as a crude oil or natural gas) from the reservoir.

BACKGROUND OF THE INVENTION

Crude oil is the world's main source of hydrocarbons that are used asfuel and petrochemical feedstock. To enhance recovery of crude oil orother hydrocarbons from subterranean reservoirs, various methods fortreating such reservoirs can be employed, known generally as “welltreatments.” Well treatments can include a wide variety of methods thatmay be performed in oil and gas wells, such as drilling, completion, andworkover methods. In this regard, drilling, completion, and workovermethods can include, but are not limited to, drilling, fracturing,acidizing, logging, cementing, gravel packing, perforating, andconformance methods. Many of these well treatments are designed toenhance and/or facilitate the recovery of desirable fluids from asubterranean well.

One example of a well treatment is well stimulation, which generallyrefers to any of several post-drilling processes that are used to cleanthe wellbore, enlarge channels, increase pore space in the interval tobe injected, and/or to otherwise make it possible for fluids to movemore readily into and through the wellbore, its surrounding formation,and/or the reservoir. Indeed, in some cases, well stimulation processesare used to increase the productivity of a well, such as by removingdamage in the vicinity of the wellbore or by superimposing a highlyconductive structure onto the subterranean formation.

One commonly used stimulation technique is hydraulic fracturing alsoknown as “hydraulic fracturing.” In this technique, a pressurizedfracturing fluid (or hydraulic fracturing fluid) is used to create orpropagate fractures that extend from the wellbore into reservoirformations so as to stimulate the potential for increased production, ascompared to production prior to, or without, hydraulic fracturing. Thefracturing fluid is typically injected into the formation at asufficiently high pressure such that is creates and/or extends afracture into the formation. Typically, when the pumping of thehydraulic fracturing fluid is finished, the fracture “closes” or reducesin size. Thus, the loss of fluid to surrounding permeable rock resultsas the fracture is reduced in width. In some cases to prevent fracturesfrom closing, a propping agent (or a proppant), which can be suspendedin the hydraulic fracturing fluid, is used to “prop” or hold open thefractures that has been created, after the hydraulic pressure used togenerate the fractures has been released.

Another example of a conventional method for treating a subterraneanreservoir to enhance oil recovery (typically after the natural drive ofthe reservoir has decreased) is water flooding. In some cases, thistreatment includes injecting water into the bottom of a formation oractive well to increase the pressure within a reservoir and to stimulateproduction. In some cases, water flooding can also have the effect ofdriving or displacing hydrocarbons from a reservoir toward a productionwell.

While the aforementioned methods for treating subterranean reservoirsmay be useful for enhancing hydrocarbon recovery, such methods are notnecessarily without their shortcomings. Accordingly, it would be animprovement in the art to augment or even replace current techniqueswith other techniques.

SUMMARY

This invention relates to systems and methods for increasing productionfrom a hydrocarbon containing reservoir. More specifically, someimplementations of the invention relate to the use of one or moreelectrolyzed aqueous solutions (such as electrolyzed acidic water and/orelectrolyzed alkaline water) for treating a subterranean reservoircontaining a hydrocarbon, such crude oil, and/or natural gas. While thedescribed electrolyzed aqueous solutions (or electrolyzed water) can beused to treat a wellbore or subterranean reservoir in any suitablemanner, in some non-limiting implementations, such solutions are used toimprove hydraulic fracturing, water flooding, well stimulation,drilling, and other processes that can improve recovery of a hydrocarbonfrom the reservoir.

In some non-limiting implementations, the described systems and methodsare used for hydraulic fracturing of a subterranean reservoir containinghydrocarbons. While such implementations can be carried out in anysuitable manner, in some cases, they include injecting a hydraulicfracturing fluid into the subterranean reservoir, wherein the fracturingfluid includes electrolyzed water. Although the electrolyzed water cancomprise electrolyzed acidic water or electrolyzed alkaline water, insome cases, the electrolyzed water comprises electrolyzed alkalinewater. Additionally, in some non-limiting implementations, thefracturing fluid, which includes electrolyzed water, also includes aproppant, such as a conventional sand, gel, foam, or slickwater-basedproppant.

In other non-limiting implementations, the described systems and methodsinclude using electrolyzed water for water flooding a hydrocarboncontaining reservoir to improve recovery of hydrocarbons therefrom.Generally, such implementations include injecting electrolyzed water(e.g., electrolyzed alkaline water) into an injection well and drivinghydrocarbons in a corresponding hydrocarbon containing reservoir to aproduction well, where the hydrocarbons can be recovered.

In still other non-limiting implementations, the described systems andmethods include injecting electrolyzed water into a wellbore to improvefluid flow within (or to otherwise stimulate) the wellbore and/orcorresponding reservoir.

While the described systems and methods may be particularly useful forhydraulic fracturing, water flooding, and well stimulation, thedescribed electrolyzed water (and its associated systems and methods)can be used for a wide variety of other well treatments, including,without limitation, for pre-hydraulic fracturing treatments,post-hydraulic fracturing treatments, for use as a carrying agent forone or more materials that are to be injected into a well (e.g., aproppant, cross-linker, polymer, biocide, corrosion inhibitor, pHmodifier, water flow inhibitors, etc.), as a pad, for down-holedecontamination techniques, with water-based drilling fluids, and for avariety of other uses that can increase hydrocarbon recovery from asubterranean reservoir. Additionally, while the described systems andmethods are described for use with hydrocarbon containing reservoirs,such systems and methods may be used in any other suitable application,including, without limitation, to stimulate groundwater wells,geothermal applications, to precondition or induce rock to cave inmining, etc.

These features and advantages of the present invention will become morefully apparent from the following description and appended claims, ormay be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL DRAWINGS

In order that the manner in which the above-recited and other featuresand advantages of the invention are obtained and will be readilyunderstood, a more particular description of the invention brieflydescribed above will be rendered by reference to specific embodimentsthereof that are illustrated in the appended drawings. Understandingthat the drawings depict only typical embodiments of the invention andare not therefore to be considered to be limiting of its scope, theinvention will be described and explained with additional specificityand detail through the use of the accompanying drawings in which:

FIG. 1 depicts a flowchart of a representative embodiment of a methodfor using electrolyzed water to treat a subterranean, hydrocarboncontaining reservoir; and

FIG. 2 depicts a flowchart of a representative embodiment of a methodfor using electrolyzed water to effectuate hydraulic fracturing.

DETAILED DESCRIPTION OF THE INVENTION

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,”“another embodiment,” and similar language throughout this specificationmay, but do not necessarily, all refer to the same embodiment.Additionally, the singular forms “a”, “an” and “the” include pluralreferents, unless the context clearly dictates otherwise.

Furthermore, the described features, structures, or characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. In the following description, numerous specific details areprovided, such as examples of suitable additives, techniques for usewith electrolyzed water, electrochemical cells, electrolyzed aqueoussolutions, proppants, hydraulic fracturing fluids, etc., to provide athorough understanding of embodiments of the invention. One havingordinary skill in the relevant art will recognize, however, that theinvention may be practiced without one or more of the specific details,or with other methods, components, materials, and so forth. In otherinstances, well-known structures, materials, or operations are not shownor described in detail to avoid obscuring aspects of the invention.Also, ranges may be expressed herein as from (or between) about oneparticular value, and/or to about another particular value. When anysuch a range is expressed, it is to be understood that anotherembodiment is from the one particular value and/or to the otherparticular value, along with all suitable combinations and sub-rangeswithin said range.

The described systems and methods relate generally to generating one ormore electrolyzed aqueous solutions (such as electrolyzed acidic waterand/or electrolyzed alkaline water) and then introducing such solutionsinto a subterranean reservoir and/or wellbore in order to increase orotherwise facilitate recovery of hydrocarbons from the well. While suchsystems and methods can be used in any suitable manner, FIG. 1 shows onenon-limiting embodiment of a typical method 100 for using anelectrolyzed aqueous solution to treat a subterranean reservoircomprising hydrocarbons.

While each of the methods described herein (as well as any portionthereof) can be modified in any suitable manner (including byrearranging, reordering, adding to, removing, modifying, substituting,and otherwise modifying various portions of the method), FIG. 1 shows anembodiment in which the method begins at step 105 by obtaining/providingwater. In this regard, the water can be obtained from any suitable watersource, including, without limitation, one or more aquifers, rivers,streams, wells, lakes, ponds, seas, oceans, reservoirs, municipal watersupplies, etc. Typically, water can obtained from a water source (e.g.,an aquifer or from the sea) and can be transported to an injection wellsite by truck or by surface facilities including pumps, filters, watertreatment equipment, and flow lines. In some embodiments, the water isstored near the site (e.g., in a pond, reservoir, tankers, etc.) andthen pumped to the electrochemical cells as needed.

In some embodiments, before being electrolyzed, the water is treated(e.g., filtered, distilled, subjected to a reverse osmosis process,etc.) to remove any undesired contaminants (e.g., chlorine, dirt,debris, silt, minerals, and/or materials).

Indeed, in some embodiments, an electrolyte (such as a salt) is added tothe feed water. In such embodiments, any suitable electrolyte can beadded to the water, including, without limitation, NaCl, LiCl, KCl, etc.In some implementations, however, NaCl is added to the water to improvethe water's ability to act as an electrolyte solution in anelectrochemical cell (discussed below). Where the water comprises a salt(e.g., NaCl), the salt can be present in the water at any suitableconcentration that allows the electrochemical cell to produceelectrolyzed alkaline water and/or electrolyzed acidic water as the cellfunctions. In one non-limiting example, salt is present in the water atbetween about a 1% and about a 50% saturation. In another example, saltis present in the water at a concentration of between about a 10% andabout a 30% saturation. In still another non-limiting example, salt ispresent in the water at a concentration between about a 15% and about a25% saturation (e.g., 20%±2%).

At step 110, FIG. 1 shows the method 100 continues as an electrochemicalcell (including any similar cell) is used to produce electrolyzed water(e.g., electrolyzed alkaline water and/or electrolyzed acidic water).While this can be done in any suitable manner, in some non-limitingembodiments, a feed water solution (e.g., a saline solution) is suppliedto an electrolytic cell that includes both an anode chamber and acathode chamber, which respectively house one or more anode electrodesand cathode electrodes, as are known in the art (e.g., dimensionallystable electrodes, ceramic electrodes, flat plate electrodes, meshelectrodes, and/or other novel or conventional electrodes).

While the cathode and electrode chambers can have any suitablerelationship with respect to each other, in some non-limitingembodiments, the two chambers are separated by a membrane (e.g., apolymer membrane, a ceramic membrane, a salt bridge, etc.) that iscapable of allowing the passage of certain ions from one chamber to theother. Indeed, in some embodiments, the present invention employselectrochemical cells having separate anode and cathode chambers, whichallow the cells to produce separate anolyte and catholyte streams.

When the water solution (e.g., saline solution) is placed in contactwith the various electrodes in the cell, electrolysis occurs once theelectrodes are electrically charged by a power source. In somenon-limiting embodiments, during the electrochemical reaction,positively charged ions (e.g., NaOH) migrate to the negative electrode(e.g., the cathode) and, in some cases, negatively charged ions (e.g.,precursors for hypochlorous acid (HOCl) or another reaction) migratetowards the positive electrode (e.g., anode). Thus, the feed watersolution can be cathodically electrolyzed in the cathode chamber toproduce electrolyzed water as an antioxidant solution called alkalinecatholyte (or electrolyzed alkaline water). The feed water solution canalso be anodically electrolyzed in the anode chamber to produceelectrolyzed water as an oxidant solution called anolyte (orelectrolyzed acidic water), whose pH is modified in the process. In someinstances, the electrolyzed acidic water is a strong oxidizing solution.More specifically, in some non-limiting embodiments in which acidicelectrolyzed water is generated through the electrolysis of a diluteaqueous sodium chloride (NaCl) solution, the Cl⁻ ions areelectrochemically oxidized to form Cl₂ gas at the anode, which gas canbe partially hydrolyzed to form hypochlorous acid (HOCl).

While the electrolyzed acidic water from the anolyte stream can have anysuitable pH less than about 7, in some embodiments, it has a pH betweenabout 1 and about 7. In some alternate embodiments the electrolyzed acidwater has a pH of between about 3 and about 6, alternatively betweenabout 2 and about 6, or alternatively between about 4 and about 6 (e.g.,between about 1.7 and about 4).

Although the electrolyzed alkaline water from the catholyte stream canhave any suitable pH greater than about 7, in some embodiments, it has apH between about 7 and about 14. In other embodiments, the electrolyzedalkaline water has a pH between about 8 and about 13, or, alternatively,between about 8 and about 12, between about 9 and about 13, betweenabout 10 and about 13, or between about 9 and about 11.

For the various processes described herein, the electrolyzed water thatis utilized can, in certain embodiments, be an electrolyzed acidicwater, and in alternate embodiments, an electrolyzed alkaline water. Inthis regard, different considerations that can be taken into account inthe decision as to use acidic or alkaline electrolyzed water can includethe type of formation to be treated, the condition of the reservoirbeing treated, the type of operation being performed, and the like.Additionally, while electrolyzed acidic water may be useful in a widevariety of applications, in some non-limiting embodiments, it may bebeneficial for use: in deactivating down-hole biologics, in acidhydraulic fracturing, in dissolving/removing fines and debris, inclearing fractures, for treating down-hole contamination, inhydrogen-sulfide containing wells, as a carrying agent, as a pad, and invirtually any other application in which the use of an acidic solutionin a wellbore, a formation, or a reservoir may be beneficial. Similarly,while electrolyzed alkaline water may be useful in a wide variety ofapplications, in some non-limiting embodiments, it is used todissolve/remove fines and debris, to clear fractures, as a carryingagent, as a pad, and for a virtually any other application in which useof an alkaline solution in a wellbore, a formation, and/or a reservoirmay be useful. Indeed, because electrolyzed alkaline water can help toimprove laminar flow, and thereby reduce emulsification, flocculation,and other perturbation of liquid flow, in some embodiments, such wateris used as a carrier to carry desired materials (e.g., proppant) to asubterranean reservoir.

Continuing with the method 100 of FIG. 1, step 115 shows the method cancontinue as the electrolyzed water (e.g., electrolyzed acidic water orelectrolyzed alkaline water) is introduced into a wellbore and/orreservoir. While this electrolyzed water can be sent to the wellboredirectly from the electrochemical cell, in some non-limitingembodiments, after the electrolyzed water is generated, it is stored(e.g., in a pond, in tankers, etc.) and then pumped to the wellbore ondemand.

While the electrolyzed water can be injected or otherwise introducedinto a wellbore/reservoir for any suitable purpose, in some non-limitingembodiments, the electrolyzed water is introduced in a hydraulicfracturing process, a water flooding process, and/or well stimulationprocess; each of which is discussed below in more detail.

In some non-limiting embodiments, the present invention provides aprocess for performing hydraulic fracture stimulation treatments (orhydraulic fracturing) in one or more reservoir formations, where one ormore of said formations are intersected by a wellbore in which, mostcommonly, a casing or liner will generally have been cemented in place(typically referred to as a “cased hole”). In this regard, FIG. 2 showsthat, in some embodiments, the hydraulic fracturing method 200 includesa first step (205) of initiating the hydraulic fracturing by firstensuring pressure communication between the wellbore and thesubterranean formation by any suitable technique, such as perforatingthe casing at the desired point of communication and, thereafter (asshown at step 215, skipping optional step 210 at this point) increasingthe wellbore pressure by pressurizing a electrolyzed-water-containingfracturing fluid (or hydraulic fracturing fluid) in the well to causethe subterranean formation to fracture.

In some cases, rapid increases of pressure at the bottom of a well cancause the formation rock to fail, causing the formation to split, andthereby creating a fracture into which the fracturing fluid can bepumped. In certain embodiments, by initiating injection of fluids in ahigher effective stress layer, the fracture height growth is notrestricted by the stresses in a bounding layer. As pumping continues,the fracture can grow, favoring increasing the fracture height, ratherthan the generation of significant fracture length. This trend cancontinue as additional hydraulic fracturing fluid is pumped into theformation.

The hydraulic fracturing fluid can have any suitable viscosity thatallows it to fracture (or to propagate fractures in) a formation as itis injected into a reservoir. In some embodiments, however, thehydraulic fracturing fluid is relatively viscous and can appeargelatinous at ambient temperature. Some non-limiting examples ofsuitable viscosities of the hydraulic fracturing fluid range from about1 to about 1,000 cp, and more typically from about 100 to about 700 cp,and most typically from about 200 to about 500 cp (e.g., between about250 cp and about 450 cp).

Where the hydraulic fracturing fluid includes electrolyzed water (e.g.,electrolyzed acidic water or electrolyzed alkaline water), the hydraulicfracturing fluid can include any suitable concentration of theelectrolyzed water that allows the hydraulic fracturing fluid to performits intended function. In some embodiments, the hydraulic fracturingfluid includes from about 1% up to 10% by volume of the electrolyzedwater. In some alternative embodiments, the hydraulic fracturing fluidincludes up about 20% electrolyzed water, or alternatively up to about30%, up to about 40%, up to about 50%, up to about 60%, up to about 70%,up to about 80%, up to about 90%, or even up to about 100% (e.g., wherepure electrolyzed water is injected directly into a formation at highpressure).

In certain embodiments, the hydraulic fracturing fluid compriseselectrolyzed acidic water. In some such embodiments, the electrolyzedacidic water for use in the hydraulic fracturing fluid has a pH of lessthan about 7, alternatively less than about 6.9, and as low as about 1.Indeed, in certain embodiments, the electrolyzed acidic water has a pHof between about 1 and about 7, alternatively between about 1.5 andabout 3, alternatively between about 2 and about 4, alternativelybetween about 3 and about 5, and alternatively between about 4 and about6. In certain other embodiments, the hydraulic fracturing fluid has a pHof between about 3.5 and about 6.5, alternatively between about 3.5 andabout 5, alternatively between about 5 and about 6.5, alternatively 2and 3, and alternatively between about 2.1 and about 2.5.

Where the hydraulic fracturing fluid comprises electrolyzed acidicwater, such water can have any suitable oxidation reduction potentialthat allows the hydraulic fracturing fluid to perform its intendedfunction. In some non-limiting embodiments, the electrolyzed acidicwater for use in a hydraulic fracturing fluid has an oxidation reductionpotential of between about 750mV and about 1400 mV, alternativelybetween about 750 mV and about 900 mV, alternatively between about 900mV and about 1100 mV, alternatively between about 900mV and about1300mV, alternatively between about 1100 mV and 1400 mV, andalternatively between about 1000 and 1200 mV.

In embodiments in which the hydraulic fracturing fluid compriseselectrolyzed alkaline water, the electrolyzed water added to thehydraulic fracturing fluid can have any suitable pH. Indeed, in somenon-limiting embodiments, the electrolyzed alkaline water has a pH ofbetween about 7.1 and about 14, alternatively between about 7.5 andabout 8.5, alternatively between about 8.5 and about 9.5, alternativelybetween about 9.5 and about 10.5, alternatively between about 10.5 andabout 11.5, alternatively between about 11.5 and about 12.5, andalternatively between about 12.5 and about 14. In certain embodiments,the electrolyzed alkaline water for use as a hydraulic fracturing fluidhas a pH greater than about 9, and alternatively greater than about 11.

Where the hydraulic fracturing fluid comprises electrolyzed alkalinewater, such electrolyzed water can have any suitable oxidation reductionpotential that allows the hydraulic fracturing fluid to perform itsintended function. Indeed, in some embodiments, the electrolyzedalkaline water in the hydraulic fracturing fluid has an oxidationreduction potential of between about −350 mV and about −1300 mV,alternatively between about −350 mV and about −600 mV, alternativelybetween about −600 mV and about −950 mV, alternatively between about−600 mV and about −980 mV, and alternatively between about −950 mV and−1300 mV.

After establishing communication with a reservoir (e.g., in a highereffective stress layer) (as discussed above with respect to step 205 inFIG. 2), in some embodiments, high pressure pumping is subsequentlystarted (as discussed above with respect to step 215). While thehydraulic fracturing fluid can be pumped into the reservoir at anysuitable pressure, in some embodiments, it is pumped at pressures of upto about 15,000 Psi, alternatively up to about 10,000 Psi, alternativelyat pressures of between about 5,000 Psi and about 15,000 Psi, andalternatively at pressures between about 5,000 Psi and about 10,000 Psi.

In some embodiments, during the pumping, a proppant (e.g., silica sand,resin-coated sand, a ceramic, a gel, a foam, and/or another proppingagent) is added to the fracturing fluid containing the electrolyzedwater. The timing of the addition and the quantity of proppant used canbe based upon any suitable factor, including, without limitation theexpected final dimensions of the fracture and the required proppantconcentration that will be needed within the fracture to achieve therequired production performance, as is known in the art. The amount offracturing fluid injected is often determined based upon the desiredsize of the fracture.

In certain embodiments (and as shown at step 210 in FIG. 2), theelectrolyzed water is optionally used as a pre-treatment fluid toprepare a wellbore and/or formation prior to a hydraulic fracturingprocess. In certain other embodiments (as shown at step 220 in FIG. 2),the electrolyzed water is optionally used as a post-treatment fluid,which is supplied to a wellbore and/or a formation after a hydraulicfracturing process has been completed. Depending upon the formation, theuse of electrolyzed water for pre-treatment and/or post-treatment offormations that are subject to hydraulic fracturing processes can helpwith the removal of fines and/or particulate material, can dissolve orbreak down certain particles or portions of the formation, and/or (whenused as a pre-treatment fluid) can improve the results of the hydraulicfracturing process.

In all uses related to the hydraulic fracturing of a formation, eitheras a pre-treatment fluid, a post-treatment fluid, or as the hydraulicfracturing fluid, the electrolyzed water can make up a portion of thefluid that is utilized and combined with other fluids or chemicals, orcan be used without the addition of other chemicals or fluids.

Turning now to water flooding, in certain embodiments of the presentinvention, electrolyzed water is used for water flooding methods. Whilesuch methods can be performed in any suitable manner, in someembodiments, such methods include introducing a sufficient amount ofelectrolyzed water (e.g., electrolyzed acidic water or electrolyzedalkaline water) and at a sufficient pressure into a formation (e.g., thebottom of a formation, through an injection well (or wells)) to drivehydrocarbons from the formation (e.g., via a production well (orwells)), where the hydrocarbons are recovered.

While water flooding can be performed at any suitable stage in theexistence of a reservoir, in some embodiments, the well injectioncomposition described herein is used in a flooding operation (e.g., assecondary flooding, as opposed to a primary recovery operation whichrelies on natural forces to move the fluid) to recover a productionfluid (e.g., oil from a subterranean formation). The flooding can alsobe repeated one or more times to increase the amount of production fluidrecovered from the reservoir. In subsequent flooding operations, theinjection fluid can be replaced with a fluid that is miscible orpartially miscible with the oil being recovered.

In certain embodiments, the injection well can include a cement sheathor column that has been positioned or created in the annulus of awellbore, wherein the annulus is disposed between the wall of thewellbore and a conduit, such as a casing, running through the wellbore.Thus, the compositions described herein can pass through the casing intothe subterranean formation during flooding.

Where the flooding process includes the use of electrolyzed acidicwater, such water can have any suitable pH that allows the floodingprocess to be used to recover hydrocarbons from a reservoir. In someembodiments, the electrolyzed acidic water used for water floodingprocesses has a pH as low as about 1 and has high as about 7, oralternatively as high as about 6.9. In certain embodiments, however, theelectrolyzed acidic water has a pH of between about 1 and about 3,alternatively between about 2 and about 4, alternatively a between about3 and about 5, alternatively between about 4 and about 6. In still otherembodiments, the electrolyzed water used for water flooding processeshas a pH of between about 3.5 and about 6.5, alternatively between about3.5 and about 5, alternatively between about 5 and about 6.5,alternatively between about 2 and about 3, and alternatively betweenabout 2.1 and about 2.5.

Where the electrolyzed water used for water flooding compriseselectrolyzed acidic water, such water can have any suitable oxidationreduction potential that allows the flooding process to recoverhydrocarbons. In some embodiments, the electrolyzed acidic water usedfor water flooding processes has an oxidation reduction potential ofbetween about 750 mV and about 1400 mV, alternatively between about 750mV and about 900 mV, alternatively between about 900 mV and about 1100mV, alternatively between about 900 mV and about 1300 mV, andalternatively between about 1100 mV and 1400 mV. In certain embodiments,the electrolyzed acidic water has an oxidation reduction potential ofbetween about 1000 and 1200 mV.

In embodiments in which the flooding process uses electrolyzed alkalinewater, such water can have any suitable pH. In some embodiments, theelectrolyzed alkaline water used for water flooding processes has a pHof between about 7.1 and about 14, alternatively between about 7.5 and8.5, alternatively between about 8.5 and about 9.5, alternativelybetween about 9.5 and about 10.5, alternatively between about 10.5 andabout 11.5, alternatively between about 11.5 and about 12.5, andalternatively between about 12.5 and about 14. In still otherembodiments, the electrolyzed alkaline water for water flooding has a pHgreater than about 9, and alternatively greater than about 11.

In embodiments in which electrolyzed alkaline water is used for a waterflooding process, such water can have any suitable oxidation reductionpotential. In some embodiments, the electrolyzed alkaline water has anoxidation reduction potential of between about −350 mV and about −1300mV, alternatively between about −350 mV and about −600 mV, alternativelybetween about −600 mV and about −950 mV, and alternatively between about−950 mV and −1300 mV.

The water injected into the injection well can include any suitableconcentration of electrolyzed water. In some embodiments, the floodingwater comprises up to about 20% by volume electrolyzed water (e.g.,electrolyzed acidic or alkaline water), alternatively up to about 30% byvolume electrolyzed alkaline water, alternatively up to about 40% byvolume electrolyzed water, alternatively up to about 50% by volumeelectrolyzed water, alternatively up to about 60% by volume electrolyzedwater, alternatively up to about 70% by volume electrolyzed water,alternatively up to about 80% by volume electrolyzed water, andalternatively up to about 90% by volume electrolyzed water. In certainembodiments, pure electrolyzed water is used for water flooding.

In certain embodiments, the apparatus used for water flooding includesat least one pump for supplying water from holding means, such as apond, or the like to the electrochemical cell. In some embodiments, theapparatus includes at least one pump for supplying electrolyzed waterfrom the electrochemical cell to the reservoir.

With reference now to well stimulation, according to the describedsystems and methods, well stimulation is a process that is conducted toimprove the flow of hydrocarbons from a reservoir into the wellbore, andtypically includes the injection of electrolyzed water (e.g.,electrolyzed acidic water or electrolyzed alkaline water) along withvarious chemicals into the wellbore and/or formation.

In some embodiments in which well stimulation includes the use ofelectrolyzed acidic water, such water can have any suitable pH. In someembodiments, the electrolyzed acidic water used for well stimulation hasa pH of less than about 7, alternatively less than about 6.9, and as lowas about 1. Indeed, in certain embodiments, the electrolyzed acidicwater has a pH of between about 1 and about 7, alternatively betweenabout 1.5 and about 3, alternatively between about 2 and about 4,alternatively between about 3 and about 5, and alternatively betweenabout 4 and about 6. In certain other embodiments, the electrolyzedwater for well stimulation has a pH of between about 3.5 and about 6.5,alternatively between about 3.5 and about 5, alternatively between about5 and about 6.5, alternatively about 2 and about 3, and alternativelybetween about 2.1 and about 2.5.

Where the electrolyzed water used for well stimulation compriseselectrolyzed acidic water, such water can have any suitable oxidationreduction potential. In some embodiments, the electrolyzed acidic waterused for well stimulation has an oxidation reduction potential ofbetween about 750 mV and about 1400 mV, alternatively between about 750mV and about 900 mV, alternatively between about 900 mV and about 1100mV, alternatively between about 900 mV and about 1300 mV, andalternatively between about 1100 mV and 1400 mV. In certain embodiments,the electrolyzed acidic water has an oxidation reduction potential ofbetween about 1000 and 1200 mV.

In some embodiments in which the described well stimulation process useselectrolyzed alkaline water, such water can have any suitable pH. Insome embodiments, the electrolyzed alkaline water used for wellstimulation processes has a pH of between about 7.1 and about 14,alternatively between about 7.5 and about 8.5, alternatively betweenabout 8.5 and about 9.5, alternatively between about 9.5 and about 10.5,alternatively between about 10.5 and about 11.5, alternatively betweenabout 11.5 and about 12.5, alternatively between about 12.5 and about14. In still other embodiments, the electrolyzed alkaline water used forwell stimulation has a pH greater than about 9, and alternativelygreater than about 11.

In embodiments in which electrolyzed alkaline water is used for wellstimulation processes, such water can have any suitable oxidationreduction potential. In some embodiments, the electrolyzed alkalinewater has an oxidation reduction potential of between about −350 mV andabout −1300 mV, alternatively between about −350 mV and about −600 mV,alternatively between about −600 mV and about −950 mV, and alternativelybetween about −950 mV and −1300 mV.

In certain embodiments, the electrolyzed water can be injected into thewellbore of a production well to remove all or a portion of the fines orother particulate matter that may be present. In alternate embodiments,the electrolyzed water is injected to remove or reduce the formation ofscale deposits within the wellbore.

In certain embodiments, the well stimulation fluids include polymers,such as a soluble polysaccharide. In certain embodiments, the polymercan be included to increase the viscosity of the fracturing fluid, whichcan aid in the creation of a fracture, and thicken the aqueous solutionso that solid proppant particles can be employed and delivered to thefracture.

In certain embodiments, one or more of the described well treatmentfluids (i.e., for well stimulation or any other technique) includes atleast one polymer. In some embodiments, the classes of polymers arepolysaccharides or synthesized polymers. Some non-limiting examples ofsuitable polymers include galactomannan polymers and derivatizedgalactomannan polymers; starch; xanthan gums; hydroxycelluloses;hydroxyalkyl celluloses; polyvinyl alcohol polymers (e.g., homopolymersof vinyl alcohol and copolymers of vinyl alcohol and vinyl acetate); andpolymers (e.g., homopolymers, copolymers, and terpolymers) that are theproduct of a polymerization reaction comprising one or more monomersselected from the group consisting of vinyl pyrrolidone,2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and acrylamide,methacrylic acid, styrene sulfonic acid, acrylamide and other monomerscurrently used for oil well treatment polymers, among others. In certainembodiments, the polymer comprises a polyvinyl alcohol polymer preparedby hydrolyzing vinyl acetate polymers. In some embodiments, the polymeris water-soluble. Specific polymers that can be used include, but arenot limited to, hydrolyzed polyacrylamide, guar gum, hydroxypropyl guargum, carboxymethyl guar gum, carboxymethylhydroxypropyl guar gum,hydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose,hydroxypropyl cellulose, copolymers of acrylic acid and acrylamide,xanthan, starches, and mixtures thereof, among others.

In certain embodiments, the well stimulation fluids (or otherelectrolyzed water containing solutions) include one or more additives,such as water, oils, salts (including, but not limited to, organicsalts), cross-linkers, polymers, biocides, corrosion inhibitors anddissolvers, pH modifiers (e.g., acids and bases), breakers, metalchelators, metal complexors, antioxidants, wetting agents, polymerstabilizers, clay stabilizers, scale inhibitors and dissolvers, waxinhibitors and dissolvers, asphaltene precipitation inhibitors, waterflow inhibitors, fluid loss additives, chemical grouts, diverters, sandconsolidation chemicals, proppants, permeability modifiers, viscoelasticfluids, gases (e.g., nitrogen and carbon dioxide), and foaming agents.While such additives can serve any suitable function, in someembodiments, they are included to enhance the stability of the fluidcomposition and to prevent breakdown caused by exposure to oxygen,temperature change, trace metals, constituents of water added to thefluid composition, and to prevent non-optimal cross-linking reactionkinetics.

In certain embodiments, the electrolyzed water used for well stimulationis capable of removing debris in the wellbore. In other embodiments, theelectrolyzed water is used to dissolve particulate material within thewellbore. In some embodiments, the well stimulation fluids are supplieddirectly to a desired location (e.g., using tubing, such as coiledtubing).

The described systems and methods can be modified in any suitablemanner. In example, the electrolyzed water (e.g., electrolyzed acidicwater or electrolyzed basic water) is optionally combined with one ormore additives, such as nanoparticles having certain desired propertiesfor stimulation, flooding, and/or fracturing. In this regard, desiredproperties can include, without limitation, properties relating toreduction of friction, biocides, oxygen scavengers, formation control,scale inhibition, and the like. In some embodiments, the additives,including the nanoparticle additives, can assist with the separation ofvarious fluids, such as hydrocarbon and/or oil-based fluids and water.

In another example, the described electrolyzed water can be used withany other fluid or chemical used in the recovery of hydrocarbons from areservoir. By way of non-limiting example, the described electrolyzedwater can be used in water-based drilling fluids.

The various aspects of the invention described herein can be practicedindependently or together. Thus, in certain embodiments, one of skill inthe art may use electrolyzed alkaline water for one or more hydraulicfracturing, water flooding, and/or well stimulation processes.Additionally, the described processes can each be repeated, asappropriate.

In certain embodiments, the use of the electrolyzed water for thevarious processes described herein, including use for pre-treatment ofwells and/or formations for hydraulic fracturing processes, as acomponent for hydraulic fracturing processes; for the post-treatmentafter hydraulic fracturing processes; for use in well stimulation; foruse in removing or reducing the presence of fines, particulate matter,and/or scale formation; for water flooding; or for use in water-baseddrilling fluids, can be effective in reducing the surface tension withinthe entire well, including within the formation, within the wellbore,and from the source of the water (including feed water and/orelectrolyzed water) which can be tanker, trucks, holding tanks,reservoirs, ponds, etc. In certain embodiments, the electrolyzed water(e.g., electrolyzed alkaline water) can be particularly useful inreducing the tension within the wellbore. Use of the electrolyzed waterscan also be effective for the reduction of friction within theformation, within the wellbore, and in the components utilized fortransporting the water, including, without limitation, tanker trucks,pumps, and holding tanks.

While specific embodiments and examples of the present invention havebeen illustrated and described, numerous modifications come to mindwithout significantly departing from the spirit of the invention.Additionally, the described embodiments and examples are all to beconsidered in all respects as being illustrative only and notrestrictive in any manner. The scope of the invention is, therefore,indicated by the appended claims, rather than the foregoing description.All changes that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A method for treating a subterranean, hydrocarbon containingreservoir, the method comprising: using an electrochemical cell togenerate an electrolyzed aqueous solution; and introducing theelectrolyzed aqueous solution into the subterranean, hydrocarboncontaining reservoir.
 2. The method of claim 1, wherein the electrolyzedaqueous solution comprises electrolyzed alkaline water.
 3. The method ofclaim 1, wherein the electrolyzed aqueous solution compriseselectrolyzed acidic water.
 4. The method of claim 1, wherein the methodcomprises a process selected from hydraulic fracturing of thesubterranean, hydrocarbon containing reservoir; water flooding thesubterranean, hydrocarbon containing reservoir; and improving fluid flowof the subterranean, hydrocarbon containing reservoir, a wellbore of aproduction well, or an injection well.
 5. A method for the hydraulicfracturing of a subterranean, hydrocarbon containing reservoir, themethod comprising: using an electrochemical cell to generate anelectrolyzed aqueous solution; and injecting a hydraulic fracturingfluid into the hydrocarbon containing reservoir, wherein the hydraulicfracturing fluid comprises the electrolyzed aqueous solution.
 6. Themethod of claim 5, wherein the electrolyzed aqueous solution compriseselectrolyzed alkaline water.
 7. The method of claim 5, wherein theelectrolyzed aqueous solution comprises electrolyzed acidic water. 8.The method of claim 5, wherein the hydraulic fracturing fluid furthercomprises a proppant.
 9. The method of claim 6, wherein the electrolyzedalkaline water has a pH of greater than about
 9. 10. The method of claim7, wherein the electrolyzed acidic water has a pH of between about 2 andabout
 6. 11. A method for water flooding a subterranean, hydrocarboncontaining reservoir to improve recovery of the hydrocarbons from thereservoir, the method comprising: using an electrochemical cell togenerate an electrolyzed aqueous solution; injecting the electrolyzedaqueous solution into the subterranean reservoir to drive thehydrocarbons in the hydrocarbon containing reservoir to a productionwell; and recovering hydrocarbons from the production well.
 12. Themethod of claim 11, wherein the electrolyzed aqueous solution compriseselectrolyzed alkaline water.
 13. The method of claim 12, wherein theelectrolyzed alkaline water has a pH greater than about
 9. 14. Themethod of claim 11, wherein the electrolyzed aqueous solution compriseselectrolyzed acidic water.
 15. The method of claim 14, wherein theelectrolyzed acidic water has a pH of between about 2 and about
 6. 16. Amethod for improving fluid flow within a wellbore of a production well,the method comprising: using an electrochemical cell to generate anelectrolyzed aqueous solution; and supplying the electrolyzed aqueoussolution to the wellbore such that the electrolyzed aqueous solutionreacts with debris in the wellbore.
 17. The method of claim 16, whereinthe electrolyzed aqueous solution comprises electrolyzed alkaline water.18. The method of claim 17, wherein the electrolyzed alkaline water hasa pH greater than about
 9. 19. The method of claim 16, wherein theelectrolyzed aqueous solution comprises electrolyzed acidic water. 20.The method of claim 19, wherein the electrolyzed acidic water has a pHof between about 2 and about 6.